Age-related macular degeneration (AMD) is the leading cause of blindness among patients over 65 years of age in industrialized nations (C. J. Lee et al., Biomaterials, 27:1670-1678 (2006); J. T. Lu et al., Biomaterials, 28:1486-1494 (2007)). Evidence has been shown that AMD is usually associated with the dysfunction of retinal pigment epithelial (RPE) cells and the degeneration of underlying Bruch's membrane. Human Bruch's membrane is a thin (2-4 μm in thickness), compact layer of collagen fibers located between the retina and vascular choroid, and it is semipermeable to allow the transports of nutrients and other macromolecules from the underlying blood vessels to retina. Directly on the Bruch's membrane is a monolayer of hexagonally shaped RPE cells that interface with photoreceptors. On the apical surface of polarized RPE cells, microvilli are developed for the interdigitation of RPE cells with the photoreceptor outer segments. One theory postulates that, in AMD, RPE cells stop degrading the waste products from photoreceptors properly, leading to the accumulation of wastes in Bruch's membrane (C. J. Lee et al., Biomaterials, 27:1670-1678 (2006); J. T. Lu et al., Biomaterials, 28:1486-1494 (2007)). As a result, Bruch's membrane may become clogged and thickened, and its composition can change with lower permeability to nutrients, which can cause the dysfunction of RPE cells, the loss of photoreceptors, and ultimately severe vision loss.
Direct transplantation of healthy RPE cells to replace the diseased ones was once considered as a potential treatment. However, it was proven later to be difficult because sometimes the transplanted RPE cells failed to adhere and form a monolayer on the diseased Bruch's membrane (C. J. Lee et al., Biomaterials, 27:1670-1678 (2006 T. Lu et al., Biomaterials, 28:1486-1494 (2007)).
What is needed in the art are new ways to transplant retinal pigment epithelial cells as well as other cells. More etticatious treatments for age-related macular degeneration and other diseases are also needed. The present invention satisfies these and other needs.